Disclosed are inhibitors of post-proline cleavage enzymes, such as inhibitors of dipeptidyl peptidase IV, as well as pharmaceutical compositions thereof, and methods for using such inhibitors. In particular, the inhibitors are improved over those in the prior art by selection of particular classes of side chains in the P1 and/or P2 position of the inhibitor. The inhibitors can have a better therapeutic index, owing in part to reduced toxicity and/or improved specificity for the targeted protease.
